Focal length of a concave lens is 25 cm. Calculate its power.
25 D
-0.25 D
-4 D
-10 D
4 D
Focal length of a concave lens is 400 cm, then power of the lens is:
A beam of light travelling parallel to the principal axis of a concave lens appears to diverge from a point 25 cm behind the lens after refraction. Calculate the power of the lens.